Silvio Berlusconi's enthusiasm for cosmetic surgery is well documented, but it was not previously known to extend to either genitalia or classical sculpture.

Government officials confirmed today, however, that a valuable statue of the god Mars, on loan to the prime minister's office, had been fitted with an artificial penis. The original was chipped off at some stage in its long life, beginning in AD175.

La Repubblica said the transplant was carried out at Berlusconi's "express request" and that, along with a new hand for an accompanying statue of the goddess Venus, it had cost the Italian taxpayer €70,000 (£60,000).

But Mario Catalano, the prime minister's architect, told the Guardian: "I took the decision."

He said he had agreed the operation with the heritage ministry and that it had "not cost a lira" because it was carried out by restorers employed by the government.

"There are two philosophies of restoration," he said. "One is just to clean the work and leave it as it is. The other involves making the work whole again, without damaging it, to provide an image of the work as it was originally conceived."

He said the missing part had been attached to the original with a magnetic system, but was unable to say exactly how it worked. Both the hand and the prosthetic penis were removable.

The prime minister had approved the finished work and had the statue put in a prominent position at the entrance to his official residence in Rome, Palazzo Chigi.

It is not the first time Berlusconi has been accused of interfering with art works. Two years ago, government employees veiled the breasts of a nude in a mural that featured prominently behind the prime minister during press conferences.